This invention relates to resolver-type positioning apparatus for a rotary drive system.
In known resolver-type positioning apparatus for a rotary drive system, a frequency division counter is used to produce an exciting voltage signal having sinusoidal or rectangular waveform from a clock pulse, and the exciting voltage signal is supplied to the primary winding of a resolver coupled to the rotary drive system, for example an electric motor. Furthermore, a up-down counter is used to produce a reference signal from the clock pulse and a feed pulse so as to drive a predetermined amount the rotary drive system based on a phase difference between the reference signal and an output produced by the secondary winding of the resolver.
With this system, since the resolution of the resolver is determined by the frequency of the clock pulse and the up-down counter, it is necessary to increase the frequency of the clock pulse in order to improve the resolution. However, since there is a upper limit for the clock pulse frequency the improvement of the resolution is also limited.